1. Field of the Invention
The present general inventive concept relates generally to a method of controlling an image processing apparatus, and more particularly to a method of controlling an image processing apparatus to improve reduction quality of an image by improving visibility of a black character, and an apparatus to carry-out the method.
2. Description of the Related Art
In general, an image processing apparatus converts a document created by a user who wishes to perform printing through an application program or an image photographed by a user using a digital camera into coded data to print the data to a recording paper so that the user can see the data. Such an image processing apparatus typically includes a printer, a scanner, a copy machine, or a facsimile.
An image processing apparatus capable of performing color printing includes toners of various colors such as cyan, magenta, yellow, and black (CMYK). The color image is then printed out by combining colors of the toners.
After the color image is binarized, black pixels are expressed by a combination of the C, M, Y, and K colors, which may cause toner dispersion or noise around an edge of the color image during reproduction. Furthermore, when such a combination is used, the obtained black color is different from the original black color because the level of the obtained black color is lower than the level of the original black color. As a result, reproduction quality deteriorates.
For this reason, as disclosed in U.S. Pat. No. 6,937,756, the pixels that belong to a black line image are printed using the K color to enhance a black image. That is, a K channel is enhanced and C, M, and Y channels are suppressed in order to increase the black level.
However, when an input image is scanned, the edge pixels of a black character are commonly blurred. This means that only a part of the edge pixels are determined to be the edge pixels of the black character. As a result, the printed character and thin lines may appear thicker than the originals and/or may be printed out with lower resolution.